Method for detecting dewatering load in washing machine and washing machine control method using the same

ABSTRACT

A method for detecting a dewatering load in a washing machine and a washing machine control method using the same are provided. The dewatering load is detected, and the washing machine is controlled accordingly, by first determining an acceleration or deceleration time and applying the principle that the laundry load during dewatering corresponds to the time required for accelerating/decelerating a washing tub driven by a motor, to drive the washing tub at a predetermined rotational speed based on the detection or to stop its rotation based on a determination of an overload condition. The control method includes steps of initiating a dewatering step, by driving the washing tub from a first predetermined rotational speed to a second predetermined rotational speed; detecting a load amount present in the driven washing tub, using the principle that the load amount corresponds to a time required for the driving of the washing tub from the first predetermined rotational speed to the second predetermined rotational speed; determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; comparing the determined time lapse with a reference value in a lookup table; and performing dewatering based on the detected load amount, wherein the dewatering is performed at a predetermined maximum dewatering speed corresponding to the detected load amount and wherein the dewatering is interrupted if the detected load amount exceeds a predetermined reference value. The second predetermined rotational speed may be a steady rotational speed, whereby the driving of the washing tub is performed by accelerating the washing tub by applying a constant motor torque. Alternatively, the first predetermined rotational speed may be the steady rotational speed, whereby the driving of the washing tub is performed by decelerating the washing tub by way of freewheeling the motor, applying dynamic braking, or applying anti-phase braking.

[0001] This application claims the benefit of Korean Application No. 10-2002-0085806 filed on Dec. 28, 2002, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a washing machine, and more particularly, to a method for detecting a dewatering load in a washing machine and a washing machine control method using the same, in which the dewatering load is detected and the washing machine is controlled accordingly, by first determining an acceleration or deceleration time and applying the principle that the laundry load during dewatering corresponds to the time required for accelerating/decelerating a washing tub.

[0004] 2. Discussion of the Related Art

[0005] Generally speaking, a washing machine is an apparatus for cleaning an object such as laundry and typically employs a washing tub in which the laundry and a predetermined amount of water is rotated under the control of a microcomputer using an algorithm set according to a selected wash course to perform in sequence washing, rinsing, draining, and dewatering steps. The washing tub is driven at a predetermined speed for each step. A contemporary washing machine may use any one of several drive and control techniques for rotating the washing tub to perform the above steps, including transferring a rotational force via a belt-and-pulley linkage to a dewatering shaft to rotate the tub, transferring a rotational force via a belt-and-pulley linkage to a washing shaft to rotate a pulsator or drum, controlling the speed of a BLDC motor, to rotate the tub at two different speeds (for washing and dewatering), separately controlling a power transfer path of a BLDC motor, to rotate a pulsator at a first speed (for washing) and rotating the pulsator and tub at a second speed (for dewatering), and performing “penetration” washing, by pumping a current of water into the tub while rotating the tub or wash vanes.

[0006] In particular, dewatering is performed at a much higher speed than washing, such that the washing machine may exhibit “striking,” which is a phenomenon whereby rotation is performed in an overloaded condition, such that the washing tub strikes adjacent surfaces of the washing machine during high-speed rotation, generating undue vibration, excessive noise, and even system damage. To guard against striking, dewatering speed should be carefully controlled, and in the event of an overload condition, dewatering should be stopped (aborted), since dewatering without accurate dewatering load detection may result in improper dewatering, i.e., improper speed or duration, or may cause damage to the system due to immoderate operation. Therefore, to enhance system stability and reliability, a method is needed for the accurate detection of the dewatering load before the execution of high-speed rotation of the washing tub to perform dewatering.

SUMMARY OF THE INVENTION

[0007] Accordingly, the present invention is directed to a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

[0008] An object of the present invention, which has been devised to solve the foregoing problem, lies in providing a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which accurately detects dewatering load and controls the washing machine accordingly, by first determining an acceleration or deceleration time and applying the principle that the laundry load during dewatering corresponds to the time required for accelerating/decelerating a washing tub driven by a motor, to drive the washing tub at a predetermined rotational speed based on the detection or to stop its rotation based on a determination of an overload condition.

[0009] It is another object of the present invention to provide a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which accurately detects a dewatering load before the execution of high-speed rotation of the washing tub to perform dewatering.

[0010] It is another object of the present invention to provide a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which prevents the occurrence of striking during dewatering.

[0011] It is another object of the present invention to provide a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which controls the dewatering speed based on a dewatering load detected before the execution of high-speed rotation of the washing tub to perform dewatering, by comparing the detected dewatering load with a predetermined value.

[0012] It is another object of the present invention to provide a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which interrupts or aborts the execution of dewatering in the event of an overload condition.

[0013] It is another object of the present invention to provide a method for detecting a dewatering load in a washing machine, and a washing machine control method using the same, which enhances system stability and reliability.

[0014] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from a practice of the invention. The objectives and other advantages of the invention will be realized and attained by the subject matter particularly pointed out in the specification and claims hereof as well as in the appended drawings.

[0015] To achieve these objects and other advantages in accordance with the present invention, as embodied and broadly described herein, there is provided a method for detecting a dewatering load in a washing machine having a washing tub driven by a motor. The detection method comprises steps of driving the washing tub from a first predetermined rotational speed to a second predetermined rotational speed; determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; and comparing the determined time lapse with a set of reference values in a lookup table.

[0016] In one embodiment of the present invention, the second predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by accelerating the washing tub by applying a constant motor torque. In another embodiment, the first predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by decelerating the washing tub by means of one of freewheeling the motor, applying dynamic braking, and applying anti-phase braking.

[0017] In another aspect of the present invention, there is provided a method for controlling a washing machine having a washing tub driven by a motor. The control method comprises steps of initiating a dewatering step, by driving the washing tub from the first predetermined rotational speed to the second predetermined rotational speed; detecting a load amount present in the driven washing tub, using the principle that the load amount corresponds to a time required for the driving of the washing tub from the first predetermined rotational speed to the second predetermined rotational speed; and performing dewatering based on the detected load amount.

[0018] Preferably, the control method further comprises steps of determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; and comparing the determined time lapse with a reference value in a lookup table, wherein the dewatering is performed at a predetermined maximum dewatering speed corresponding to the detected load amount and wherein the dewatering is interrupted if the detected load amount exceeds a predetermined reference value.

[0019] It is to be understood that both the foregoing explanation and the following detailed description of the present invention are exemplary and illustrative and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

[0021]FIG. 1A is a graph plotting the rotational speed of a washing tub, during the execution of dewatering in a washing machine adopting the method of the present invention, according to a first embodiment;

[0022]FIG. 1B is a graph plotting the rotational speed of a washing tub, during the execution of dewatering in a washing machine adopting the method of the present invention, according to a second embodiment; and

[0023]FIG. 2 is a graph illustrating the relationship between washing tub speed and laundry load during dewatering, for explaining the principle of the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0025] Referring to FIGS. 1A and 1B, respectively illustrating a dewatering load detection and control method according to first and second embodiments of the present invention, a load amount is detected in a washing machine having a washing tub driven by a motor to perform dewatering by a high-speed rotation of the washing tub. At the time of initiating a dewatering step, and before the high-speed rotation of the washing tub, the washing tub is controlled to be driven from a first predetermined rotational speed to a second predetermined rotational speed, and the elapsed time required for the above driving of the washing tub is determined. Thereafter, the load amount is obtained by comparing the determined time lapse with a set of reference values in a lookup table recording a predetermined set of known laundry load amounts. That is, a predetermined maximum dewatering speed is set for each laundry load amount. The lookup table may be stored in a memory of the microcomputer of the washing machine.

[0026] In the first embodiment of the present invention, the second predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by accelerating the washing tub by applying a constant motor torque. In the second embodiment, the first predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by decelerating the washing tub by means of one of freewheeling the motor, applying dynamic braking, and applying anti-phase braking. The dewatering load detection method of the present invention uses the principle that the laundry load during dewatering corresponds to the time required for accelerating/decelerating the washing tub. That is, the accelerating/decelerating time is proportional to an inertial force acting on the load, and the inertial force is proportional to the load amount.

[0027] In detecting a dewatering load to perform dewatering in a washing machine adopting a first embodiment of the method of the present invention, the washing tub is accelerated as shown in FIG. 1A to obtain an acceleration time Δt1 and thereby detect the dewatering load before proceeding the dewatering. In detecting a dewatering load to perform dewatering in a washing machine adopting a second embodiment of the method of the present invention, the washing tub is decelerated as shown in FIG. 1B to obtain a deceleration time Δt2 and thereby detect the dewatering load before proceeding the dewatering. According to the present invention, the dewatering load may be accurately detected based on either the acceleration or deceleration, but a more reliable detection can be achieved by obtaining both the acceleration time Δt1 and the deceleration time Δt2. In such a case, acceleration preferably precedes deceleration since deceleration requires a higher initial speed.

[0028] Referring to the method illustrated in FIG. 1A, using washing tub acceleration, a washing tub is driven by a motor upon the initiation of a dewatering step, whereupon the initial rotational speed of the washing tub is substantially zero. Thereafter, the washing tub is accelerated to a predetermined steady rotational speed, by applying a constant motor torque, and an elapsed time is measured to obtain an acceleration time Δt1 required for the tub speed to reach a state of steady rotation. The acceleration time Δt1 is measured from the point of initiating the acceleration, which may be a stopped state or a predetermined slow rate of rotation. The difference between the initial speed and the predetermined steady rotational speed after acceleration is an acceleration value Δrpm1. The dewatering load is detected as a direct result of obtaining the acceleration time Δt1. That is, the acceleration time Δt1 corresponds to a known laundry load amount referenced in the lookup table, to indicate a predetermined maximum dewatering speed for the laundry load amount. Then, the drive of the washing tub is controlled according to the predetermined maximum dewatering speed most appropriate for the detected dewatering load. In the event that the detected dewatering load exceeds a predetermined reference value, an overload condition is determined so that the dewatering step may be interrupted or aborted.

[0029] Referring to the method illustrated in FIG. 1B, using washing tub deceleration, a washing tub is driven by a motor upon the initiation of a dewatering step, such that a predetermined steady rotational speed before deceleration is reached. Thereafter, the washing tub is decelerated to a predetermined rotational speed, and an elapsed time is measured to obtain a deceleration time Δt2 required for the tub speed to reach the predetermined decelerated rotational speed from the point of initiating the deceleration. The difference between the predetermined steady rotational speed before deceleration and the predetermined decelerated rotational speed is a deceleration value Δrpm2. The dewatering load is detected as a direct result of obtaining the deceleration time Δt2. That is, the deceleration time Δt2 corresponds to a known laundry load amount referenced in the lookup table, to indicate a predetermined maximum dewatering speed for the laundry load amount. Then, the drive of the washing tub is controlled according to the predetermined maximum dewatering speed most appropriate for the detected dewatering load. In the event that the detected dewatering load exceeds a predetermined reference value, an overload condition is determined so that the dewatering step may be interrupted or aborted.

[0030] Here, deceleration can be achieved by any one of turning off the motor (freewheeling), dynamic braking, or anti-phase braking. In freewheeling the motor, the application of electrical power to the motor may be removed or an applied drive signal may have a duty ratio of zero; in dynamic braking, two of three motor phases are shorted together; and in anti-phase braking, a reverse rotational force is generated and applied by the motor.

[0031] The present invention detects an accurate load amount by a measurement of the acceleration and/or deceleration times with respect to a steady rotational speed of a washing tub undergoing a dewatering step, since the acceleration and deceleration times are each longer for larger laundry load amounts which produce larger dewatering load amounts, as demonstrated by FIG. 2. The dewatering load is then determined by referencing the measured time lapse with respect to a lookup table, and the washing tub is driven accordingly. That is, the dewatering is performed at a predetermined maximum dewatering speed corresponding to the detected load amount and is interrupted or aborted if the detected load amount exceeds a predetermined reference value indicating an overload condition. Thus, the present invention accurately detects the load amount upon initiation of a dewatering step, so that a determination can be made as to whether the dewatering should be progressed.

[0032] By adopting the present invention to a conventional washing machine, a dewatering load can be accurately detected before the execution of high-speed rotation of the washing tub to perform dewatering, so that the occurrence of striking during dewatering can be prevented to enhance system stability and reliability.

[0033] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover such modifications and variations, provided they come within the scope of the appended claims and their equivalents. 

What is claimed is:
 1. A method for detecting a dewatering load in a washing machine having a washing tub driven by a motor, the method comprising steps of: driving the washing tub from a first predetermined rotational speed to a second predetermined rotational speed; determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; and comparing the determined time lapse with a set of reference values in a lookup table.
 2. The method as claimed in claim 1, wherein the second predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by accelerating the washing tub by applying a constant motor torque.
 3. The method as claimed in claim 1, wherein the first predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by decelerating the washing tub by means of one of freewheeling the motor, applying dynamic braking, and applying anti-phase braking.
 4. A method for controlling a washing machine having a washing tub driven by a motor, the method comprising steps of: initiating a dewatering step, by driving the washing tub from a first predetermined rotational speed to a second predetermined rotational speed; detecting a load amount present in the driven washing tub, using the principle that the load amount corresponds to a time required for the driving of the washing tub from the first predetermined rotational speed to the second predetermined rotational speed; and performing dewatering based on the detected load amount.
 5. The method as claimed in claim 4, wherein the second predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by accelerating the washing tub by applying a constant motor torque.
 6. The method as claimed in claim 5, the method further comprising steps of: determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; and comparing the determined time lapse with a set of reference values in a lookup table, wherein the dewatering is performed at a predetermined maximum dewatering speed corresponding to the detected load amount and wherein the dewatering is interrupted if the detected load amount exceeds a predetermined reference value.
 7. The method as claimed in claim 4, wherein the first predetermined rotational speed is a steady rotational speed and the driving of the washing tub is performed by decelerating the washing tub by means of one of freewheeling the motor, applying dynamic braking, and applying anti-phase braking.
 8. The method as claimed in claim 7, the method further comprising steps of: determining a time lapse between the driving of the washing tub at the first predetermined rotational speed and the driving of the washing tub at the second predetermined rotational speed; and comparing the determined time lapse with a reference value in a lookup table, wherein the dewatering is performed at a predetermined maximum dewatering speed corresponding to the detected load amount and wherein the dewatering is interrupted if the detected load amount exceeds a predetermined reference value. 